NLG Compressed/Extended Proximity Sensor Fault

TASK 32-31-00-810-815-A
NLG Compressed/Extended Proximity Sensor Fault

WARNING: MAKE SURE THAT THE GROUND SAFETY-LOCKS ARE IN POSITION ON THE LANDING GEAR. MOVEMENT OF THE LANDING GEAR CAN CAUSE INJURY TO PERSONS AND DAMAGE TO THE AIRCRAFT AND/OR EQUIPMENT.

1. Possible Causes

LGCIU-1 [5GA1]
LGCIU-2 [5GA2]
PROX SNSR-NLG EXT, SYS 1 [24GA]
PROX SNSR-NLG EXT, SYS 2 [25GA]
aircraft wiring

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	MULTIMETER - STANDARD
No specific	AR	TESTER - INSULATION RESISTANCE

B. Referenced Information

REFERENCE	DESIGNATION
AMM 24-41-00-861-002	Energize the Aircraft Electrical Circuits from the External Power
AMM 32-31-00-040-003	Check of the System 2 Proximity Sensors of the Landing Gear and the Landing Gear Doors
ASM 323103
ASM 323104
AMM 32-31-71-000-001	Removal of the LGCIU
AMM 32-31-71-400-001	Installation of the LGCIU
AMM 32-31-73-000-005	Removal of the NLG Proximity-Sensors
AMM 32-31-73-400-005	Installation of the NLG Proximity-Sensors
AMM 32-69-00-740-001	BITE Check of Landing-Gear Control Interface-Unit (LGCIU) With Use of MCDU to Ensure that Continuous BITE is Operative

3. Fault Confirmation
Subtask 32-31-00-740-055-A

A. Test
(1) Make sure that the aircraft electrical circuits are energized with an external power supply AMM 24-41-00-861-002. If external power is not available, go to Para. 4. A. (1).
(2) Do a BITE test on the LGCIU 1 (2) AMM 32-69-00-740-001 and look for an 'N L/G EXT PROX SNSR' message:
(a) If the message is not shown during the BITE test, do a check for this fault on the Post Flight Report (PFR), after the next flight.

NOTE: If the message is shown on the next flight PFR, but the BITE test continues to find no fault on the ground, do the steps given in Para. 4.A.(3) thru 4.A.(8).

(b) If the message is shown during the BITE test, do the fault isolation procedure given in Para. 4.A.

4. Fault Isolation
Subtask 32-31-00-810-066-A

A. Procedure
(1) Interchange LGCIU-1 and LGCIU-2 AMM 32-31-71-000-001 and AMM 32-31-71-400-001.
(2) Do the test given in Para. 3.A.
(a) If the fault goes, replace the initial LGCIU-1 [5GA1] or LGCIU-2 [5GA2] , AMM 32-31-71-000-001 and AMM 32-31-71-400-001.
(b) Make sure that the serviceable LGCIU is installed in its initial position.
(c) If the fault continues, do the next steps.
(3) Disconnect the electrical connector from the applicable proximity sensor 24GA (25GA).
(4) Use a MULTIMETER - STANDARD and do a check of the resistance between the pins A and B of the proximity sensor PROX SNSR-NLG EXT, SYS 1 [24GA] or PROX SNSR-NLG EXT, SYS 2 [25GA] ASM 323103 ASM 323104. The resistance must be:

11 to 13 ohms for a Ferrite proximity sensor (P/N 8-484-01)
15 to 17 ohms for an all metal proximity sensor (P/N 8-933-01).

(5) On the proximity sensor, do a check of the circuit isolation:
(a) Connect the pins A and B together.
(b) Connect one test lead of the TESTER - INSULATION RESISTANCE to the pins AB and the other test lead to the case.
(c) Supply a test signal for 5 seconds and read the resistance value shown.
(d) The resistance value must be more than 400 Megohms.
(6) If there is a failure of the proximity sensor 24GA (25GA) during the tests, replace the unserviceable proximity sensor AMM 32-31-73-000-005 and AMM 32-31-73-400-005.
(7) If the tests at steps (4) and (5) are satisfactory:
(a) Do a check of the aircraft wiring between the proximity sensor 24GA (25GA) electrical connector and LGCIU-1 (2) ARINC tray ASM 323103 ASM 323104.
(b) Connect the electrical connector to the applicable proximity sensor 24GA (25GA).
(8) If there is a circuit/interface fault, do the repair.
(9) Do the test given in Para. 3.A.
(10) Do the GROUND SCANNING and make sure that the ground log is clear.
(11) If MMEL conditions apply to the PROX SNSR-NLG EXT, SYS 2 [25GA] :
(a) Do the deactivation of the proximity sensor AMM 32-31-00-040-003.

[Rev.8 from Aug 2018] 2026.04.04 04:31:20 UTC